How to make a very slim watch and keep battery life long? In this Hack-a-Gecko project, they tried to catch two birds with one stone.
We thought it would be cool to utilize the extremely low power EFM32 in combination with an extremely low power display to create a wrist watch demo application. And usually, the smaller and thinner something is, the cooler it is. (Admittedly, wrist watches do not necessarily follow this trend… big watches.)
Anyway, we wanted it slim. The starting point was the memory LCD display from Sharp (link). It is truly a Nano ampere display technology. And it is also thin, only 0.75 mm. A watch also needs a battery, cool new technologies exist such as the Thinergy battery, but the voltage of 4.1 V is a bit awkward. We decided to use a standard 3.0V CR1616 cell as it can power the EFM32 and display directly. Thickness of battery + display is 2.35 mm, is it possible to design the electronics as well within this thickness limit…? Challenge accepted!”
“The iPhone or iPod Touch has an accelerometer that detects how the device is oriented. As the devices moves off axis (from straight up and down) the screen rotates. I want to use that feedback to control the position of a motor or servo or cause specific events to happen depending on the device’s position.”
“Tonight, I overheard a couple of people who live with me in the flat talk about a person who has left 2 HP LaserJet4′s in the hallway, for more than a week. Putting them in front of his door didn’t help, and the next action they had in mind was to tape a huge angry sign on them so he perhaps would notice it. While that’s one way to do it, I decided it wouldn’t be fun and perhaps the offending person would remember it better when we did something more playful.
A nice thing about the HP laserjets is that they have a little display, and you can use PJL, a sort of controlling language, to change what’s displayed on it, using a bit of code that runs on a PC. Problem was: I didn’t have a PC connected to the laserjet, so I had to divine a standalone solution.”